// HTMLParser Library $Name: v1_6 $ - A java-based parser for HTML
// http://sourceforge.org/projects/htmlparser
// Copyright (C) 2003 Derrick Oswald
//
// Revision Control Information
//
// $Source: /cvsroot/htmlparser/htmlparser/src/org/htmlparser/filters/XorFilter.java,v $
// $Author: ian_macfarlane $
// $Date: 2006/05/16 09:11:41 $
// $Revision: 1.1 $
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//

package org.htmlparser.filters;

import org.htmlparser.Node;
import org.htmlparser.NodeFilter;

/**
 * Accepts nodes matching an odd number of its predicates filters (XOR
 * operation). For example, where it has two filters, it accepts only if and
 * only if one of the two filters accepts the Node, but does not accept if both
 * filters accept the Node.
 */
public class XorFilter implements NodeFilter {
	/**
	 * The predicates that are to be xor'ed together;
	 */
	protected NodeFilter[] mPredicates;

	/**
	 * Creates a new instance of an XorFilter. With no predicates, this would
	 * always answer <code>false</code> to {@link #accept}.
	 * 
	 * @see #setPredicates
	 */
	public XorFilter() {
		setPredicates(null);
	}

	/**
	 * Creates an XorFilter that accepts nodes acceptable to either filter, but
	 * not both.
	 * 
	 * @param left
	 *            One filter.
	 * @param right
	 *            The other filter.
	 */
	public XorFilter(NodeFilter left, NodeFilter right) {
		NodeFilter[] predicates;

		predicates = new NodeFilter[2];
		predicates[0] = left;
		predicates[1] = right;
		setPredicates(predicates);
	}

	/**
	 * Creates an XorFilter that accepts nodes acceptable an odd number of the
	 * given filters.
	 * 
	 * @param predicates
	 *            The list of filters.
	 */
	public XorFilter(NodeFilter[] predicates) {
		setPredicates(predicates);
	}

	/**
	 * Get the predicates used by this XorFilter.
	 * 
	 * @return The predicates currently in use.
	 */
	public NodeFilter[] getPredicates() {
		return (mPredicates);
	}

	/**
	 * Set the predicates for this XorFilter.
	 * 
	 * @param predicates
	 *            The list of predidcates to use in {@link #accept}.
	 */
	public void setPredicates(NodeFilter[] predicates) {
		if (null == predicates)
			predicates = new NodeFilter[0];
		mPredicates = predicates;
	}

	//
	// NodeFilter interface
	//

	/**
	 * Accept nodes that are acceptable to an odd number of its predicate
	 * filters.
	 * 
	 * @param node
	 *            The node to check.
	 * @return <code>true</code> if an odd number of the predicate filters
	 *         find the node is acceptable, <code>false</code> otherwise.
	 */
	public boolean accept(Node node) {
		int countTrue;

		countTrue = 0;

		for (int i = 0; i < mPredicates.length; i++)
			if (mPredicates[i].accept(node))
				++countTrue;

		return ((countTrue % 2) == 1);
	}
}
